The present invention relates to a resin composition that is improved in moldability, impact resistance, heat resistance, dimensional stability and stiffness or rigidity.
Liquid -crystal polyesters can be molded at comparatively low temperatures and yet they exhibit high heat resistance and are superior in mechanical properties, chemical resistance and dimensional stability. Because of these features, liquid-crystal polyesters hold much promise as materials that can be used in a broad range of applications. However, liquid-crystal polyesters are known to have their own problems such as anisotropy that occurs in their mechanical properties, shrinkage during molding, etc. on account of their high degree of orientation, as well as propensity to spalling on the surface of a molded article on account of its pronounced skin-core structure. With a view to solving these problems, it was proposed that inorganic fillers such as glass fibers (GF) and minerals be compounded into liquid-crystal polyesters [see "Journal of Materials Science", 21 (1986), pp. 2889-2900]. This method is not effective unless the filler is incorporated in a substantial amount (.gtoreq.20 vol %) but then problems arise such as the wear of the screw in the molding machine and the increase in the brittlness of the molded article. In order to solve these problems, the anisotropy of the matrix resin itself must be reduced.
In an attempt to meet this need, it has been proposed that liquid-crystal polyester resins be mixed with other ingredients to provide liquid-crystal resin compositions (see Japanese Patent Public Disclosure (KOKAI) Nos. 57-40551 and 63-6046). However, these compositions experience a marked drop in their mechanical strength properties, in particular, Izod impact strength, within the range where improved anisotropy can be attained and hence, they have not yet reached the commercial stage.
The present inventors conducted intensive studies in order to improve the impact strength of a composition consisting of a liquid-crystal polyester resin and a polycarbonate resin. As a result, they found that when a small amount of a polyolefin and/or an olefinic copolymer was added to the mixture of a liquid-crystal polyester resin and a polycarbonate resin, the heat resistance and dimensional stability of the mixture were retained and yet its impact strength was significantly improved. The present invention has been accomplished on the basis of this finding.